The International Olympic Committee stipulated that 80% of the sewage entering the Guanabara Bay be treated

With just over 500 days to go before the 2016 Olympic Games open in Rio de Janeiro, work is continuing around the clock to complete the sporting venues. But the BBC has seen startling scientific evidence which suggests a requirement to clean the city's polluted waterways in time for the Games will not be fulfilled.

From the air you can see Rio's Olympic Park, in the Barra zone to the south of the city, taking shape.

From a distance, it looks pretty spectacular but up close the view and the smell is much less appealing. With deadlines looming to complete the sporting venues, the waters around the park have been completely neglected.

Great Britain Olympic sailor Charlotte Dobson says she has found a lot of debris in the water

The chemically overloaded lime green lagoon, which surrounds it on three sides, is fed by several small jet-black rivers, full of untreated sewage.

"Every river around here is practically dead, because they are full of sewage," says the biologist Mario Moscatelli who has long campaigned against the way these once pristine lagoons have been destroyed.

Whatever your own particular "shade" of politics, it's impossible not to be impressed or beguiled by Jose "Pepe" Mujica.

There are idealistic, hard-working and honest politicians the world over - although cynics might argue they're a small minority - but none of them surely comes anywhere close to the outgoing Uruguayan president when it comes to living by one's principles.

Argentina's populist President Cristina Fernandez de Kirchner could not have had a worse start to the new year.

Her final year in office - she is not allowed to stand for re-election - already looks like it will be dominated by ongoing economic uncertainties and a political scandal involving the apparent murder of a former state prosecutor.

A cell at the Orwellian Department of Political and Social Order or DOPS

The Department of Political and Social Order or DOPS. It is a place as Orwellian and as sinister as the name suggests.

Right in the heart of the modern metropolis of Rio de Janeiro, the former police administration centre, prison and torture chamber has remained largely untouched since the end of the dictatorship in 1985.

President Dilma Rousseff (R) and challenger Aecio Neves faced off in a bruising TV debate on Friday

All votes count in Brazil - there's no "winner takes all" system as in American states - so each part of this vast country is being fought over by Dilma Rousseff and Aecio Neves ahead of Sunday's vote. Nowhere is the race closer than in the southeastern state where they were both raised, Minas Gerais.

"Minas" is among the most closely contested constituencies in this election and is one in which many features affecting voters in the wider country can be found.

The jungle state of Acre is a long way from anywhere. Tucked into the north-western corner of Brazil, it is closer to the big towns of eastern Bolivia and southern Peru than it is to the industrial heartland of southern Brazil.

Yet it is through here that many migrants looking for a better life or escaping persecution in their own countries choose to enter Brazil.

About Wyre

As the BBC's first correspondent to be based in Rio de Janeiro, Wyre has come full circle. He lived in Brazil as a child and took his degree in Latin American studies. His first foreign posting for the BBC was the Chilean capital Santiago in the mid-1990s where he covered events in Spanish-speaking South America.

Subsequent stints as the correspondent in Wales and then the Middle East have seen him cover everything from football and rugby world cups, to political scandals and the Arab uprisings. There have been far too many close shaves and lost friends along the way, but there have also been moments of levity and the unfathomable privilege of roaming the world reporting for the BBC.

A passionate Welshman, supported by his constant travelling companions - a wonderful wife and four children - Wyre now faces the daunting task of covering not only one of the most iconic cities on earth, but also the emerging political and economic superpower of Brazil, as well as pretty much anything else of interest between the Darien Gap and the Straits of Magellan.